I have a 5.5 tank... would it be okay to purchase a 30 watt heater? Here is the description:

"The HT-10 submersible heater is suitable for aquariums up to 30 gallons in size. The electronic thermostat automatically adjusts heat output to keep the water at a constant 78 degrees F. All you have to do is place in the aquarium and plug it in."

I know someone told me that for a 5.5g tank a 10-25 watt is suitable... so would it matter much buying 30w? Please help

(I'm thinking of ordering online. I have no real fish stores near me, and I don't drive :P)

Preset heaters tend to not heat the water enough or overheat the water--I would only buy one with an adjustable temperature dial. It will give you stability as well as control so you can adjust the temperature if the fish gets sick with a bacterial infection (requiring lower temps) or external parasites (requiring higher than normal temps). Adjustable ones are all-around better products. I use this one: http://www.fosterandsmithaquatics.co...8&pcatid=11368